This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: A priority in HIV vaccine development is to generate antiviral immune responses in the genital tract and rectum, where HIV transmission most frequently occurs. Recent data suggests that oral or rectal immunization will be required to induce optimal intestinal immunity in vaccine recipients. However, oral vaccines must be protected from stomach acid as well as degradative enzymes in the intestinal lumen. To determine if dual encapsulation of vaccine in liposomes and enteric-coated capsules can induce immune responses after oral delivery. Methods: Cationic liposomes containing SIV envelope protein and DNA encoding noninfectious SHIV89.6P particles were freeze-dried and placed inside enteric-coated capsules designed to resist acidic pH but not the neutral pH of the duodenum. Twelve rhesus macaques that had been previously immunized by the nasal route with SHIV DNA/SIV Env protein were orally-immunized on weeks 0 and 6 with a capsule containing liposomal DNA/protein. Results/Discussion: Strong lymphoproliferative responses to the SIV Env and Gag proteins were observed in blood of all animals 1 month after the 1st oral immunization. The frequencies of SIV Env- and Gag-specific T cells producing IFN-g and TNF-a were increased in the majority of animals after the 1st immunization, and in all animals after the 2nd immunization. There were no increases in SIV-specific mucosal or systemic antibodies. A dual encapsulation strategy utilizing cationic liposomes and enteric-coated capsules can be used successfully to deliver DNA/protein in the small intestine for induction of vaccine-specific T cells. However, generating intestinal IgA responses will require larger doses of protein or an oral adjuvant. Further studies aimed at optimizing oral HIV vaccines should be performed since regimens that utilize both the nasal and oral delivery routes are more likely to induce protective immunity in the genital tract and rectum than those that utilize the intramuscular and nasal routes.